I want to create a document with blank fillable lines(i,e., your name here). I thought I could drag the insert text box into the document and size the box to a one line input field. I click and drag insert test box to document but box is not inserted. I am able to insert a table but not text box.
Did you actually mean a Text Box control from the respective toolbar or a Text Box being of a shape subtype.
Of course there should be different naming like Text Shape and Text Control . but things are as they are - and even worse 
Therefore:
Please always consider that terms can be ambiguous in some cases, and tell as precisely as possible what you mean.
Both cases:
Icons of the kind aren’t dragable. You click one to tell what kind of object you want - and then you click and drag in the area of the document to create the object with its initial position and initial size. .
Don’t use a text box unless you’re perfectly aware of the consequences. Text boxes are primarily intended for form design. If your document is not a form but rather a “standard” paper, article or novel, you’ll head into trouble with text boxes because they don’t integrate well with the rest.
I suppose you want to enter some “floating” side note to your text. By “floating” I mean this small note is not read in continuity with the main text but is a comment or explanation similar to a foot note. Do this with a frame into which you can enter text and format it as you would do in the main flow (this is not feasible, or at least very painful with text boxes).
In case you want a fancy heading with specific formatting or “positioning”, enter your text and style it Heading n where n is the hierarchical level of the heading (1 for chapter, 2 for sub-chapter, 3 for sub-sub-chapter, …). Customize the Heading n paragraph style properties to fit your needs.
If my answer looks Klingon for you, I recommend you read the Writer Guide and especially the chapters about styles.
To show the community your question has been answered, click the ✓ next to the correct answer, and “upvote” by clicking on the ^ arrow of any helpful answers. These are the mechanisms for communicating the quality of the Q&A on this site. Thanks!
In case you need clarification, edit your question (not an answer which is reserved for solutions) or comment the relevant answer.
Please do not use Add Answer but edit your original question to enhance the details of your question (answers are reserved for solutions to a problem on this Q&A site).
If my answer looks Klingon for you
@ajlittoz, for a non-native speaker, your Klingon is nearly word-perfect 
I meant I used technical terms, such as form design, styles and even text box, which have a very specific meaning in Writer and this meaning may differ from common sense. Anyway, thanks for your kind remark.